The content of the book, "Ideal Marriage: Its Physiology and Technique," may have had something to do with the delay. Written by a Dutch gynecologist and published in 1926, the scientific sex manual is filled with graphs and diagrams, and, according to the National Review, "is not a prude's book."

It read: "We found this book amongst my late brother-in-law's things. Funny thing is, the book didn't support his efforts with his first and only marriage, it failed. No wonder he hid the book. So sorry. A shocked in-law."

The fine for an overdue book at the time was 5 cents a day, which would total more than $1,000 by now. But the library caps book late fees at $12.

"We just want to get our materials back," said managing librarian Billy Parrott.